The present invention relates to a buffer conveyor for conveying and buffering products according to the preamble of claim 1.
Buffer conveyors according to the prior art are known in a great many versions thereof. U.S. Pat. No. 5,413,213 shows two types of buffer conveyors. The first type is shown in FIGS. 1-4 and FIGS. 7, 8. The buffer conveyor in question comprises a single conveyor 10 belt, which winds in double helical paths from the lower end and from the upper end, with the paths from the lower end forming the first and the second conveyor. The paths from the upper end form an inoperative part of the buffer conveyor. The first conveyor blends into the second conveyor at the upper end in that the 15 conveyor belt is lifted off its guide and moves back onto the guide of the first conveyor via the transfer unit at the second conveyor. The location where the conveyor belt is lifted off its guide can be varied along the length of the first (and thus also the second) conveyor, as a result of which the buffering length 20 is varied, which is compensated in the inoperative part of the conveyor belt {a compensation loop}. A drawback of said construction is that the construction in which the conveyor belt, which is under a tensile force, is to be moved onto and off the guide construction, is complex partially on account of the 25 compensation loop that is required, whilst it is furthermore not very advantageous for technical (driving) reasons to drive one entire, long conveyor belt.
These drawbacks are eliminated in the second type of buffer 30 conveyor shown in FIGS. 5 and 6 of U.S. Pat. No. 5,413,213. In said type of buffer conveyor, two helically wound conveyor belts are nested together, so that the windings of the first and the second conveyor extend parallel to each other, one above another. The transfer unit is mounted on a column and comprises two transfer elements in the form of chain conveyors, one for removing products from the first conveyor and one for transferring products to the second conveyor. The transfer from one chain conveyor to the other chain conveyor takes place via a chute, and it will be understood that such a transfer unit can only be used with certain types of products, in this case cigarettes.
U.S. Pat. No. 6,152,291 shows yet another type of conveyor. Here, two conveyor belts are used for forming the first and the second 10 conveyor, which extend parallel to each other in the helical path. The transfer unit is guided in the space between the first conveyor and the second conveyor for transferring the products from the first conveyor to the second conveyor and for moving along the first and the second conveyor for adjusting the 15 buffering length. Said buffer conveyor has the drawback that the products are subject to an abrupt change of direction in the transfer unit. Not all products are unaffected by this. Furthermore, longer products cannot be transferred with the transfer unit.